The endogenous neuromodulator adenosine acts extracellularly via activation of specific membrane-bound receptors called P1-purinoceptors. These adenosine receptors are divided into four subclasses, A1, A2A, A2B and A3 receptors. All four classes are coupled to the enzyme adenylate cyclase. Activation of the adenosine A1 and A3 receptors can lead to an inhibition of adenylate cyclase, while activated A2A and A2B receptors can stimulate adenylate cyclase. The adenosine receptors are ubiquitously distributed throughout the body, and can modulate diverse physiological functions, including induction of sedation, relaxation of smooth muscle and vasodilation. Activation of these receptors by adenosine can therefore be of importance in many disease states. Accordingly, blocking these receptors can produce an effect leading to the prevention or treatment of many diseases. For example, the A2A adenosine receptor antagonists are reported to have a beneficial effect on neurodegenerative diseases such as Parkinson's disease.1 In recent years, a number of new and interesting ligands, which block the various adenosine receptor subtypes, have been synthesised. These ligands encompass bi- and tri-cyclic heteroaromatic systems—featuring 3-nitrogen tri-cyclic systems (e.g., the imidazoquinolines);2 4-nitrogen tri-cyclic systems (e.g., triazoloquinoxalines);3 6-nitrogen tri-cyclic systems (e.g., the pyrazolotriazolopyrimidines);4 2-nitrogen bi-cyclic systems (e.g., the naphthyridines);5 and 3-nitrogen bi-cyclic systems (e.g., deazaadenines).6 